Position sensors employing light as a measure offer a passive, nonconductive solution to the electromagnetic interference and space problems in aircraft and other control systems that require lightweight, interference tolerant sensors. Presently, these systems have undesirable aspects of high cost and complexity.
Several position sensing systems employing optical fiber based, electrically passive methods have been developed. Perhaps the most mature design is the one employing digitally encoded face plates to impress a binary pattern of light into a fiber signal channel. This method requires parallel fibers for each binary channel. To achieve the desired resolution and range, many fibers must be used. These have the advantage of being inherently digital and therefore noise immune without suffering performance degradation. Other methods involve amplitude encoding of one or more channels, which produce problems where connector or link variations occur. Still other methods include time domain and wavelength multiplexing. See U.S. Pat. No. 4,546,466 for an example of an optical encoder.
What is needed is a different sensing method with simplified optical hardware and where loss variations in the channel do not have a primary impact on system performance.